Photogrammetry

Photogrammetry is the first remote sensing technology ever developed, in which geometric properties about objects are determined from photographic images. Historically, photogrammetry is as old as modern photography itself, and can be dated to mid-nineteenth century. Photogrammetry has been defined by ASPRS as the art, science, and technology of obtaining reliable information about physical objects and the environment through processes of recoding, measuring and interpreting photographic images and patterns of recorded radiant electromagnetic energy and other phenomena.

At VMR, our primary photogrammetric expertise is in Aerotriangulation, and Digital Mapping and Edit. We utilize our experience and talent in these areas to provide the most accurate and detailed mapping available.

Softcopy Aerotriangulation is a routine, in which the GPS ground control is loaded, then the fiducials on the digitally scanned photograph are measured and interior orientation is computed. The system then selects and measures all passpoints and tiepoints. The relative orientation is computed and will show all residuals on the points measured. The final output from the bundle adjustment will supply all of the parameters that are needed to set up the softcopy stereo equipment for the ensuing topographic mapping.

All Softcopy AT at VMR is performed utilizing the Z/I ISAT triangulation package mounted on a Z/I ImageStation photogrammetric workstation. ImageStation ISAT is an exceptional automatic triangulation package that delivers the best-matched multi-ray tie points by using robust built-in bundle adjustment during all phases of the image matching operation.

A digital terrain model (DTM) is the basis for all contouring, orthophotography, TIN calculations and other surface modeling. The DTMs collected on the Z/I workstations are comprised of mass points and breaklines; which delineate various terrain defining features, such as ravines, ridges, tops and toes of slopes, as well as mass elevation grid points used in flatter areas. Unless client specified, VMR always collects a full DTM on every project to provide the most accurate surface model possible in order to meet and exceed NMAS and ASPRS Class 1 accuracies.